Circuit interrupting apparatus



May 18, 1943 H. A. 'rRlPLE'rT CIRCUIT 4IN'IERRUPI':NG' APPARATUS Filed Dec. 30, 1940 4 Sheets-Sheet 2 f INVENTOR. am vez. ffgozeff ma. hm wif@ .TZ/ne' frz cpg/cles 60 SLI/cies per second.

BY C* z//l/ /v//.// Ou May 18, 1943 H. A. TRIPLETT CIRCUIT INTERRUPTING APPARATUS Filed Dec. 30, 194() 4 Sheets-Sheet 3 H. A. TRIPLETT CIRCUIT INTERRUPTING APPARATUS May 1.8, 1943 4 Sheets-Sheet 4 Filed Dec. 30, 1940 INV ENTOR.

Patented May 18,1943

CIRCUIT INTERRUPTING APPARATUS Hugh A. Triplett, Wilmette, Ill., asslgnor to Schweitzer & Conrad, Inc., Chicago, Ill.. a corporation of Delaware Application December 30, 1940, Serial No. 372,217

14 Claims.

This invention relates, generally, to circuit lnterrupting apparatus, and it has particular relation to such apparatus used for interrupting relatively large amounts of power in high voltage alternating current circuits.

An object of this invention is to provide a simple and relatively inexpensive condenser construction for high'voltage, high power circuit interrupting devices.

Another object of this invention is to provide for increasing the inertia of the movable terminal of a fuse of the blast action arc extinguishing type so as to reduce the effect of the blast pressure thereon when the fuse blows in moving the terminal.

Still another object of this invention is to provide for indicating'that a fuse has operated in a new and improved manner.

It is also an object of this invention to provide for releasing a gas into an arc confining passageway for assisting in extinguishing the arc and also scavenging thewalls of the passageway.

It is another object of this invention to provide for discharging two serially connected blast type of circuit interrupters at their adjacent ends when they are placed in end-to-end relation.

(Cl. 20G-120) Other objects of this invention will, in part, be

obvious and in part appear hereinafter.

VFor a more complete understanding of the nature and scope of this invention, reference Vcan be had to the following detailed description taken in connection with the accompanying drawings in which:

Figure 1 is a view, in side elevation, of one embodiment of the present invention, showing the weight in the position that it occupies after the device has operated so as to indicate that this has occurred;

Figures 2, 3 and 4, taken together and placed end-to-end, with Figure 2 on top, Figure 3 in the middle, and Figure 4 at the bottom, constitute a longitudinal sectional view of the circuit interrupter shown in-Figure 41, the device being shown y houses a condenser.

modified form of construction of the lower portion of the device shown in Figures 2, 3, and 4;

Figure 9 is a detail view showing the construction of the upper end of the rod-like terminal for the device shown in Figure 8, and how the fusible and strain elements are connected thereto;

Figure 10 is a longitudinal sectional view showing certain details of construction different from those shown in Figure 8;

Figure 11 is a view in side elevation of a pair of serially connected blast action circuit interrupting devices arranged to discharge at their adjacent terminals which are clamped together so that the devices are placed end-to-end;

Figure 12 is a longitudinal sectional view, taken generally along the line |2-l2 of Figure il, of one of the devices shown in Figure 11, and a. portion of the other device; and 'I Figure 13 is a detail longitudinal sectional View taken at right angles to the direction in which the view in Figure 12 is taken, and showing in more detail how the adjacent terminals are clamped together.

Referring now particularly to Figure 1 of the drawings, it will be observed that the reference character l0 designates, generally, one form of circuit interrupting device constructed in accordance with the present invention. 'I'he circuit interrupter l0 comprises a housing ll of suitable insulating material, such as glass or porcelain. It is provided with radially extending corrugations l2 for increasing the creepage distance over its surface. At its ends, line terminals I3 and I4 are provided which, it will be understood, are arranged to be placed in suitable contact cllps, not shown, that are connected to the line conductors. The line terminals I3 and I4 are longitudinally slotted as indicated at l5 and i6 for the reason set forth in McMahon et al. Patent No. 2,207,813. 'Ihe upper line terminal I3 is provided with an integrally formed extension ll which, as-will hereinafter appear,

the upper end o! the extension l1 and permits the exhaust of the same on opening under cerfrom it projects a weight 20 when the device has ation of the device shown in Figures 2, 3, and 4,

employing diierent means for electing the movement of the rod-like terminal;

Figure 8 is a longitudinal sectional view of a operated to indicate that such action has taken place. It will be understood that the circuit interrupter i0 is arranged tobe mounted in a vertical position so as to permit the weight 20 to drop downwardly under the inuence of gravity. Y

AIn Figures 2, 3, and 4 oi the drawings, the de- A valve I8 serves to close tails of construction of the circuit interrupter I are more clearly set forth. As there shown, a replaceable fuse cartridge, indicated generally at 24, is arranged to be inserted through the upper line terminal I3. The fuse cartridge 24 includes an insulating sleeve formed by an outer layer 25 of suitable material, such as a phenolic condensation product, and an inner layer 26 of suitable material, such as ber. The sleeve 25--26 serves to hold a mass 21 of solid arc extinguishing material, such as boric acid or magnesium borate, which, for convenience, is preferably employed in the form of rings. The mass 21 of solid arc extinguishing material provides a longitudinally extending bore 28 therethrough in which a rod-like terminal 29 of copper or the like is mounted for movement. The terminal 29 `has connected to its upper end a strain element 39 and a fusible element 3| which are connected, respectively, to arms 32 and 33 extending radially inwardly from an upper cartridge terminal 34 that is threaded on the upper end of the insulating sleeve 25-26. A iianged fitting 35 is threaded onto the cartridge terminal 34, as shown, and it bears against the upper line terminal I3 so as to have good contact engagement therewith. A metallic sleeve 3B bears against the anged terminal 35, and it carries a condenser, shown generally at 31, for cooling and condensing the blast discharged from the fuse cartridge 24 on blowing of the strain and fusible elements 30 and 3l.

The condenser 31 is preferably formed of a single strip 38 of sheet metal, such as copper,

which is spirally wound and is placed in the methe adjacent turn so as to space the turns apart.

It is then unnecessary to provide any additional ently resilient contact fingers The contact fingers 5| possess sufiici'ent resiliency to provide relatively good vcontact engagement with the metallic sleeve 49. This contact construction is employed since it is not feasible to manufacture the fuse device I0 to extremely close tolerances. That is, the distances between the line terminals I3 and I4 may vary slightly bcause of variations in the length of the housing II. Accordingly, while the upper cartridge terminal 34 maybe considered to always occupy a given position, the lower cartridge terminal provided by the metallic sleeve 49 may occupy slightly different positions longitudinally with respect to the lower line terminal I4. By providing the contact; clip 50 with the inherently resilient contact iingers 5I it is possible to take care of slight differences in position of the lower cartridge terminal 49 with respect to the lower line terminal I4, and still provide good contact engagement therebetween. As shown in Figure 4 of the drawings, the contact clip 50 is held in position by the guide tube I9 which is threaded into the lower end of the lower line terminal I4.

As shown in Figure 3 of the drawings, the

weight is fastened to the lower end of the rodlike terminal 29 and is movable therewith down- I wardly when the strain and fusible elements spacing means between the successive turns of the spiral.

The extension I1 is closed by'a cap 40 which is threaded thereon as indicated in Figure 2. The cap 40 carries the valve I8 which is mounted on a valve stem 4I- that is slidably mounted in the cap 40. The valve I8 serves to close apertures 42 and 43 in the cap 40, and is held in the closed position by a coil compression spring 44 surrounding the valve stem 4I. It will be understood that the valve I8 remains closedunder the influence of the spring 44 until a predetermined pressure is reached in the chamber containing the condenser 31. This pressure is then suilicient to lift the valve i8 against the biasing force of the spring 44 and permits the discharge of the blast to the atmosphere through the apertures 42 and 43.

At the lower end of the insulating sleeve 25- 26 of the fuse cartridge 24 there is provided a metal fitting 48 which is threaded into the sleeve, as shown. A metallic sleeve 49, forming a lower cartridge terminal, is threaded onto the tting 48, and it is of suiiicient length to extend downwardlythrough the lower line terminal I4. Contact engagement with the metal sleeve 49 is provided by a generally ring-like contact clip 59 which is provided with integrally formed inherthe opening in the same,

and 3I (Figure 2) have blown. The mass of the Weight 20 substantially increases the inertia of the movable parts, including the rod-like terminal 29 so that the pressure which is exerted on the upper end of the rod-like terminal 29 on blowing of the strain and fusible elements 30 and 3| is substantially ineffective to move it downwardly. The rod-like terminal 29 then falls through the bore 28 substantially only under the influence of gravity. This is desirable so as to expose a minimum of the bore 28 to the heat of the arc that is formed between the rod-like terminal 29 andthe upper cartridge terminal 34 on blowing of the strain and fusible elements 30 and 3|. As a result, lower pressures are generated within the device because of the arc, and consequently, the likelihood of the circuit interrupter I0 being blown to pieces is materially reduced.

With a view to interconnecting the weight 20 and rod-like terminal 29 with the lower cartridge terminal formed by the metallic sleeve 49, a ilexible conductor 52 is coiled about the upper end of the weight 20 and the lower end of the rod-like terminal 29. As shown, the conductor 52 is secured at its upper end in the metallic fitting 48 and, at its lower en d, in the upper portion of the weight 20.

As shown in Figure 4 of the drawings, a cap 53 isthreaded onto the lower end of the guide tube I9. A frangible disc or diaphragm 54 is secured by a split ring 55 on the cap 53 for closing When the strain and fusible elements 30 and 3I have blown, the rodlike terminal 29 moves downwardly together with It will be noted that the metallic sleeve 49,

Figure 3, is provided with a threaded aperture 58 which registers with a groove 59 in the weight 20.

The threaded aperture 58 ls adapted to receive a set screw 60, Figure 6, when the cartridge 24 is outside of the housing Il. The set screw 30 serves to clamp the weight securely against the opposite wall of the sleeve 49 so as to prevent breakage of the strain wire during shipment and handling of the cartridge 24. The set screw 60 is arranged to project beyond the sleeve 49 far enough to prevent insertion of the cartridge 24 into the housing Il until it is removed thereby insuring that it will be withdrawn before the circuit interrupter I0 is re-iused.

When the circuit interrupter I0 is to be refused, it is first removed from its terminal clips. The cap is then removed together with the condenser 31. The guide tube I9 is then unscrewed from-the lower line terminal l4,`where upon the cartridge 24 can be withdrawn through the upper line terminal I3. These steps are reversed in inserting an unblown fuse cartridge.

In Figure 7 of the drawings, curve 6I shows the relationship between the movement of the rodlike terminal 29 with respect to time as measured in cycles per second of alternating current. The curve 6l represents the speed at which the rodlike terminal 29 moves when it is biased by a spring under certain predetermined conditions. It will be observed that, after a slight initial movement, its movement bears a straight line relationship with respect to time. Thus, during the first few cycles after the strain and fusible element 30 and 3| have blown, relatively great movement of the rod-like terminal 29 in the bore 23 takes place. This exposes a considerable area of the bore 28 to the heat of the arc, and considerably more arc extinguishing medium may be evolved therefrom than is necessary for extinguishing the arc.

Curve 62 in Figure 'l of the drawings shows the relationship between the movement of the rodlike terminal 29 and the frequency of a Gil-cycle alternating current source when the rod-like terminal 29 follows the law of a freely falling body. From curve 62 it will be observed that, during the first few cycles, only a relatively small movement of the rod-like terminal 29 takes place. As a result, during these first few cycles during which, experience indicates, most arcs are extin-- guished, only a relatively small amount of the arc extinguishing material 21 is exposed to the heat of the arc and, consequently, considerably less pressures are generated in the device.

In Figures 8 and 9 of the drawings there is shown a construction which can be employed in lieu of certain parts of the construction shown in Figures 2, 3, and4 of the drawings. In Figures 8 and 9 of the drawings, a hollow rod-like terminalv 63 has been substituted for the solid rod-like terminal 29 previously described. 'I'he hollow rod-like terminal 63 has a passageway B4 extending longitudinally therethrough which is closed at its upper end by a metal cap 85, preferably formed of silver, which is arranged to receive the lower ends of the strain and fusible ele ments 30 and 3l. The cap 95 is calibrated so as to melt or fuse under different current conditions and open the upper end of the passageway 94,

The lower end of the passageway 54 in the rod-like terminal 63 opens into a reservoir, shown generally at B6, which is arranged to hold a gas, such as carbon dioxide or helium, -under pressure. The reservoir Sl comprises upper and lower hollowmembers 61 and il which are threaded together, as shown. A valve 99 is provided in the lower member 68 to provide for ing the same under pressure. After the reservoir 6B has been filled, the lower end of the valve B9 can be dipped in solder so as to seal it completely and avoid any likelihood of the escape of gas from the reservoir G6.

'I'he upper member 61 of the reservoir 66 is provided with a flanged section 1D in which the lower end of the exible conductor 52 is fastened. It also is provided with aninclined shoulder 1| that is arranged to engage the similarly inclined shoulder 51 on the cap 53 for limiting the downward movement of the reservoir 66 when the strain and fusible elements 30 and 3l have blown.

A groove 12 is provided at the upper end of the member 58 for receiving the set screw 60 through the threaded aperture 58 as previously described.

It will be understood that, under certain conditions--such as the blowing of the strain and fusible elements 30 and 3| under relatively light overload conditions-the cap 65 at; the upper end of the hollow rod-like terminal 63 may not be fused suiliciently to permit exhaustion of the gas in thev passageway 64 and the reservoir 66.

However, on flow of sufcient current in the arc that is formed, the cap ss will be melted and the gas will be permitted to flow endwise into the arc between the upper end of the rod-like terminal 63 and the upper cartridge terminal 34 so as to assist in blowing the same out and filling the arc space with a non-conducting medium. In addition, the gas flowing out of the upper end of the rod-like terminal 63 serves to provide a scavenging action on thewalls of the bore 28 in the solid arc extinguishing material 21 to free them from deposits of conducting particles which may lower the' leakage resistance over the surface of the solid arc extinguishing material 21 after the device has operated.

Preferably, the reservoir 4Sli is marie suflciently` heavy so that it can function in the same manner as the weight 20, Figure 3, previously described, and increase the inertia of the Amoving parts so that the downward reaction of the blast hassubstantially no eieet in driving the rod-like terminal 63 downwardly.

In Figure 10 of the drawings there is shown a construction which is modified somewhat from that shown in Figure 8 of the drawings. It will be understood that the construction of the upper end of the hollow rod-like terminal 63 in Figure 10 is the same as shown in Figure 9, and that for the remaining parts of the device the construction vis the same as shown in Figure 2 of the drawings.

In Figure 10 of the drawings a fitting 15 is provided on the lower end oi the sleeve 25-26 of the fuse cartridge that is somewhat different from the fitting 48 shown in Figures 3 and 8 of the drawings. The tting 15 is arranged to receive a ring-like contact clip 16 having integral- 1y formed, inherently flexible contact fingers 11 that are arranged to have contact engagement with an inclined contact surface 18 of a metallic cap 19 forming a part of a gas reservoir shown generally at 80. It will be observed that the contact ilngers 11Y provide for directly interconnecting the rod-like terminal 63 and the lower cartridge terminal which is formed by the metallic sleeve 49. Because of this, a iiexible conductor 3l having a relatively small cross-sectional area can be employed for interconnecting the tting 15 and the cap 19 to complete the circuit between the rod-like terminal 63 and the filling the reservoir li with the gas and for holdlower cartridge terminal 49 while .the former is moving after the strain and fusible elements 30 and 3| have blown. For illustrative purposes, only the end portions of the flexible conductor 9| are shown, the intermediate portion being omitted to show the adjacent details of construction more clearly.

It will be noted that the reservoir 80 includes a hollow section 82 which forms the major-p0rtion thereof.

The downward movement of the rod-like terminal 63 and the reservoir 80 is limited by a shoulder 83 on the cap 19 which is arranged to engage the inclined shoulder 51 on the cap 53. It will be observed that `the guide member 8| shown in Figure l of the drawings is somewhat shorter than the guide member |9 shown in Figures 4 and 8 of the drawings.

The upper end of the section-82 has a groove 95 for receiving 'the set screw l0 through the threaded aperture 58 as previously set forth.

Referring now particularly to Figure 11 of the drawings, it will be observed that two circuit interrupting devices, shown generally at 89 and 89, are mounted inend-tend relation.b As will hereinafter appear, the fuse devices 88 and 89 are connected intseries circuit relation and are arranged to provide two breaks or gaps in the circuit on the occurrence of an overload. The devices 88 and 99 can be mounted vertically, as illustrated, or they can be mounted in a horizontal position if desired. v

Each of the devices 88 'and 89 includes an insulating housing 90 and 9|., formed of glass or porcelain, and each has corrugations 92 and k93 for increasing the length of the creepage path over its surface. Terminals 9| and 95 are provided at the ends of the housing 90, and terminals 96 and 91 are provided at the ends of the housing 9|. It will be understood that terminals 94 and 91 are line terminals, and that terminals 95 and 96 are provided in order to -permit the series connection .of the devices. and 89. The line terminals 94 and 91 are provided with `longitudinal slots or grooves 88 and 99 which are for the same purpose as the slots or.: grooves l5 and I6 in the line terminals I3 and Il'showntin Figure 1 of the drawings and described hereinbefore.

Each of the terminals 95 and 98 has a flange |03 and |04 integrally formed therewith which are arranged to be juxtaposed so as to provide good contact engagement therebetweemand they are held in this position by screws |05, as shown in Figures 1l and 13 of the drawings.

tween is materially reduced as compared toV a A construction in which the devicedischarges ad'- jacent one line terminal. Also, the likelihood of a dash-over to an adjacent circuit is reduced.

Within each of the insulating housings and 9| there is provided a replaceable fuse cartridge.

Since the fuse cartridges are duplicates of each other, it is necessary to describe only one of them. The fuse cartridge indicated generally at H2 in Figure 12 of the drawings is illustrative of the cartridge that can be employed for both of the devices 88 and 89.

The replaceable fuse cartridge ||2 includes a sleeve ||3 of insulation. such as ber or a phenolic condensation product, and it contains a mass vH4 of solid arc extinguishing material such as boric acid or magnesium borate which lis preferably in the form of rings and provides a bore ||5 extending longitudinally therethrough. Terminals ||6 and ||1 are provided at the ends of the sleeve ||3. It will be noted that the terminal ||1 is threaded into the terminal carried by the insulating housing 9|). A bridge ||8 is secured to the terminal ||1 to which a fusible element ||9 is connected. One end of the fusible element I|9 is secured in acontact screw |20 that is threaded into the bridge |l8. It will be noted that the fusible element ||9 extends entirely through the bore ||5 and is secured to the terminal I3 by means of a set screw |2| which is inserted in a suitable tapped opening.therein.

The terminal I6 is provided with an extension |25 in the form of a metallic tube which forms a reservoir for gas under pressure, such as carbon dioxide or helium. The end of the sleeve |25 opposite the terminal ||6 is closed by a threaded plug |28 which has an aperture |21 therein through which the gas can be introduced into the reservoir. The gas is introduced through a suitable inlet |28 which, as shown, is afterward crimped over to prevent the escape of gas therethrough. If desired, the inlet |28 maybe dipped in solder to further insure that the reservoir is sealed.'

The metal sleeve |25 not only forms a reser voir for gas, but also it forms a terminal for the replaceable fuse cartridge ||2 in order to connect the same to the line terminal 94. A cap |29, threaded onto the line terminal 94 and into engagement with one end of the metallic sleeve |25, provides the necessaryinterconnection with good contact engagement between the interi'ltting parts.

It is, of course, desirable to retain the gas in the reservoir ||2 under pressure until the fusible element ||9 blows. For this purpose, a guide sleeve |30 vextends from the terminal 6 in alignment with the bore I|5 in the solid arc extinguishing material ||4. The sleeve |30 is closed at one end by a cap |3| and a frangible disc |32. Within the guide tube |30 is a plunger |33 having a knife edge |34 for rupturlng the disc or diaphragm |32. A coil compression spring |35 is provided Within the guide tube |30 for biasing the plunger |33 to rupture the disc or diaphragm |32. The plunger |33 is restrained from movement by a pair of strain wires |35 which are secured at one end to a pin |31 extending transversely across the plunger |33. At their other ends, as shown in Figure 13, the strain wires |38 are secured to the contact screw |20 to which one end of the fusible element |I9 is also secured.

It will be understood that, as long as the fusible element ||9 remains intact, the strain wires |38 will also remain intact and the plunger |33 will be held in the position shown in Figure 12 of the drawings. On the occurrence of an overload, the fusible element ||9 is blown and the iiow of current is transferred to the strain wires |33 which are promptly blown, whereupon the plunger |33 is released for movement under the inuence of the coil compression spring |35. The knife edge I 34 ruptures the disc or diaphragm |32 and permits the ow of gas from the reservoir |25 through the guide tube |30 and the bore H5. 'I'his flow of gas assists in extinguishing the arc formed in the bore ||5 and also to scavenge its walls so as to improve the dielectric properties thereof.

The blast, formed in part by the fused metal particles of the fusible element H9 and the strain wires |36, in part by the arc extinguishing medium that is evolved from the walls of the bore H5 and in part by the gas from the reservoir |25, is discharged as indicated by the arrows |38 out of the ports |01. Normally the ports |01 are closed by frangible discs or diaphragms |39 which are held in place by caps |40. The discs or diaphragms |39 are ruptured when sufficient pressure is generated by the blast on operation of the device, and thereby permit free iiow of the blast to the atmosphere.

It will be understood that both of the circuit interrupting devices 88 and 89 will be blown at the same time on the occurrence of an overload since it is intended that the fusible elements of both shall have the same operating characteristics.

Since certain further changes can be made in the foregoing constructions and different embodiments of the invention can be made without departing from the scope thereof, it is intended that all matter shown in the accompanying drawings and described hereinbefore shall be interpreted as illustrative and not in a limiting sense.

What is claimed as new is:

l. In circuit interrupting apparatus, in combination, afuse tube, a mass of solid arc extinguishing material in said tube having a relatively long narrow bore extending vertically therethrough, a relatively infusible terminal at the upper end of said bore, a rod-like terminal substantially filling and movable downwardly through said bore, fusible means interconnecting said relatively infusible terminal and the upper end of said rod-like terminal and preventing downward movement of the latter, and a weight attached to the lower end of said rod-like terminal to provide suiiicient inertia therefor so that when the same is released on blowing of said fusible means the downward reaction of the resulting blast does not materially iincrease the rate at which said rod-like terminal is accelerated over that due to the force of gravity acting alone, said weight being disposed wholly within said fuse tube as long as said fusible means remains intact and being arranged and-adapted to have at least a portion thereof project out of said fuse tube after said fusible means has blown to indicate that the same has occurred.

2. In circuit interrupting apparatus, in combination, a fuse tube, a mass of solid arc extinguishing material in said tube having a relatively long narrow bore extending vertically therethrough, a relatively infusible terminal at the upper end of said bore, 'a rod-like terminal substantially filling and movable downwardly through said bore, fusible means interconnecting said relatively infusible terminal and the upper end of said rod-like terminal and preventing downward movement of the latter, a weight attached to the lower end of ranged and adapted to disrupt said frangible closure member and to have at least a portion thereof project out of said fuse tube after said fusible means has blown to indicate that the same has occurred.

3. In circuit interrupting apparatus, in combination, a mass of solid arc extinguishing material having a bore therethrough, a stationary terminal at one end of said bore, a rod-like terminal substantially lling and movable endwise through said bore, fusible means interconnecting said terminals and adapted to be blown on the occurrence of an overload whereupon an arc is formed therebetween, and means for discharging iiuid under pressure through said rod-like terminal for assisting in extinguishing said arc and scavenging the walls of said bore.

4. In circuit interrupting apparatus, in combination, a mass of solid arc extinguishing material having a bore therethrough, a stationary terminal at one end of said bore, a rod-like terminal substantially filling and movable endwise through said bore, fusible means interconnecting said terminals and adapted to be blown on the occurence of an overload whereupon an arc is formed therebetween, a reservoir carried by and movable with said rod-like terminal for holding fluid under pressure therein, and a discharge passageway in said rod-like terminal for directing a iiowof said iluid from said reservoir into'v said arc for assisting in extinguishing it and scavenging the walls of said bore.

5. In circuit interrupting apparatus, in combination, a mass of solid arc extinguishing material having a bore therethrough, a stationary terminal at one end of said bore, a rod-like terminal substantially filling and movable endwise through said bore and having a longitudinal passageway therein closed at one end and open at the other, fusible means interconnecting said stationary terminal and the closed end of said rod-like terminal and adapted to be blown on the occurrence of an overload whereupon an arc is formed therebetween, and a reservoir carried by and movable with said rod-like terminal and communicating with said passageway therein for holding fluid under pressure, said closed `end of said rod-like terminal being adapted to be opened when the current liow through said arc generates sufficient heat to melt the same whereupon said fluid is discharged from said reservoir into said arc for assisting vin extinguishing it and scavenging the walls of said bore. y

6. In circuit interrupting apparatus, in combination, a fuse tube, a mass of solid are extinguishing-material in said tube having a relatively long narrow bore extending vertically therethrough, a relatively infusible terminal at the upper end of said bore, a rod-like terminal substantially nlling and movable downwardly through said bore and having a longitudinal passageway therein closed at its upper end and open at its lower end,

fusible means interconnecting said relatively invfusible terminal and the upper end of said rodlike terminal and preventing downward movement of the latter and adapted to be blown on the occurrence of an overload whereupon an arc is -formed therebetween, and a reservoir of substantial mass attached to the lower end of said rodlike terminal and communicating with said passageway therein for holding fluid under pressure and to provide suilicient 'inertia therefor so that when the rod-like terminal is released on blowing of said fusible means the downward reaction of the 1esulting blast does not materially increase the rate at which it is accelerated over that due to the force of gravity alone, said closed end Aof said rod-like terminal being adapted to be opened when the current iiow through said arc generates suflicient heat to melt vthe same whereupon said iluid is discharged from said reservoir into said arc for assisting in extinguishing it and scavenging the walls of said bore.

7. In circuit interrupting apparatus, in combination, terminals between which an arc may be drawn, a body of solid arc extinguishing material in confining relation to said arc and adapted to have evolved from its surface an arc extinguishing medium, a reservoir for holding fluidtherein under pressure and adapted to be placed in communication with the arc space, a frangible diaphragm sealing said reservoir, and means operable on the formation of said arc for disrupting said diaphragm to permit said fluid to ilow into said arc space for assisting in extinguishing said arc and scavenging the adjacent walls of said arc extinguishing material.

8., In circuit interrupting apparatus, in combination, a mass of solid arc extinguishingv material having a bore therethrough, terminals between Which an arc may be drawn in said bore, fusible means interconnecting said terminals, a reservoir for holding fiuid therein under pressure and adapted to be placed in communication with said bore, a frangible diaphragm sealing said reservoir, and means adapted to be released on blowing of said fusible means for rupturing said diaphragm to permit said iiuid to new into said bore for assisting in extinguishing said arc and scavenging the walls of said bore.

9. In circuit interrupting apparatus, in combination, a pair of terminals between which an arc may be drawn, one of said terminals being rodlike in character and having an aperture extending longitudinally therethrough, a body of insulating material having a bore through which said one terminal is movable to extend said arc therein, and means for discharging fluid through said aperture into said bore for assisting in extinguishing said arc.

10. In circuit interrupting apparatus, in combination, a body of insulating material having a bore with a discharge end, a pair of terminals between which an a-rc may be formed in said bore,

a reservoir for holding fluid under pressure and.

adapted to be placed in communication with the other end of said bore, frangible means sealing said reservoir, and means released on the formation of said are for rupturing said frangible means to permit said fluid to ilow through said bore and out of its discharge end to assist in vextinguishing said arc.

11. In circuit interrupting apparatus, in combination, a pair of terminals, fusible means interconnecting said terminals between which an arc is formed on blowing of said fusible means, a body of insulating material having a bore in which said arc is' formed, said bore havinga discharge end, a reservoir for holding uid under when released is in the form of an arc extinguishpressure and adapted to be placed in communication with the other end of said bore, frangible means sealing said reservoir, and means released on blowing of said fusible means for rupturing said frangible means to permit said uid to ow through said bore and out of its discharge end to assist in extinguishing said arc.l

12. In circuit interrupting apparatus. in com bination, insulating means providing a bore from the surface of which an arc extinguishing medium is adapted to be evolved due to the heat. of an arc, a pair of relatively movable terminal members between which an arc is adapted to be formed, one of said terminal members being located adjacent one end of said bore and the other being rod-like in character and movable through said bore, a reservoir for holding material which when released is in the form of an are extinguishing iluid, and means for releasing said fluid into said bore on the occurrence of an arc between said terminal members and into the space occupied by the arc for assisting in extinguishing the same and scavenging the ,walls of the bore after the arc is extinguished.

13. In circuit interrupting apparatus, in combination, insulating means providing a bore from the surface of which an arc extinguishing medium is adapted to be evolved due to the heat of an arc, a pair of relatively movable terminal members between which an arc is .adapted to be formed, one of said terminal members being 1ocated adjacent one end of said bore and the other being rod-like in character and movable through said bore, means for moving said rod-like terminal member away from the other terminal member tovextend an are drawn therebetween into said bore, a reservoir` for holding material which ing fluid, and means for releasing said uid into said bore on the occurrence of an arc between said terminal members and into the space occupied by the arc for assisting lin extinguishing the same and scavenging the walls of the bore afte the arc is extinguished.

14. A replaceable fusecartridge intended for insertion into a housing of a circuit interrupter, said cartridge comprising an insulating sleevel terminals for said sleeve, fusible means interconnecting said terminals, Weight means tensioning said fusible means and movable relative to said sleeve on blowing oflsaid fusible means for extending the arc incident thereto, and clamping means for clamping said weight means in the cartridge to prevent overstressing of said fusible means, said clamping means comprising a clamping member disposed when in operative position to prevent insertion of said cartridge into the housing of the ciicuit interrupter whereby removal of said clamping member with resulting release of said weight member and conditioned of the cartridge for operation is necessitated prior to placement of the cartridge in the interrupter housing.

HUGH A. TRIPLE'IT. 

